Radiative Destabilization in Clear-Sky Cooling Calculations

Radiative Destabilization in Clear-Sky Cooling Calculations
Hanson, Howard P.
2002-01-01 00:00:00
COMMENTS Radiative Destabilization in Clear-Sky Cooling Calculations —HOWAR D P. HANSON Atmospheric and Climate Sciences Los Alamos National Laboratory Los Alamos, New Mexico indzen et al. (2001, hereafter LCH) recently discussed observations of clouds and water vapor over the tropical oceans and concluded Lthat the earth may exhibit an "adaptive infrared iris" effect, in which tropical cloudiness and upper- tropospheric water vapor respond to changes of sea surface temperature in a manner to produce a nega- tive feedback mechanism in the climate system. LCH also discussed preliminary results that sug- gest the current generation of global climate models does not exhibit the irislike behavior observed in the satellite datasets they examined, a deficiency that needs to be addressed. This comment provides one possible source of climate-model bias that could explain some of the differences noted by LCH. This bias is analogous to that which results from ignoring the differences between cloudy and clear-air column FIG. I. (a) Top-of-the-atmosphere flux errors asso- radiative transfer. It arises due to the steep water vapor ciated with WV A aliasing. The various profiles fix gradients discussed by LCH. Because steep water stratospheric water vapor amounts down to the vapor gradients are also observed
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Abstract

COMMENTS Radiative Destabilization in Clear-Sky Cooling Calculations —HOWAR D P. HANSON Atmospheric and Climate Sciences Los Alamos National Laboratory Los Alamos, New Mexico indzen et al. (2001, hereafter LCH) recently discussed observations of clouds and water vapor over the tropical oceans and concluded Lthat the earth may exhibit an "adaptive infrared iris" effect, in which tropical cloudiness and upper- tropospheric water vapor respond to changes of sea surface temperature in a manner to produce a nega- tive feedback mechanism in the climate system. LCH also discussed preliminary results that sug- gest the current generation of global climate models does not exhibit the irislike behavior observed in the satellite datasets they examined, a deficiency that needs to be addressed. This comment provides one possible source of climate-model bias that could explain some of the differences noted by LCH. This bias is analogous to that which results from ignoring the differences between cloudy and clear-air column FIG. I. (a) Top-of-the-atmosphere flux errors asso- radiative transfer. It arises due to the steep water vapor ciated with WV A aliasing. The various profiles fix gradients discussed by LCH. Because steep water stratospheric water vapor amounts down to the vapor gradients are also observed

Journal

Bulletin of the American Meteorological Society
– American Meteorological Society